Airworthiness Directive · Amendment 39-18383 · CFM International S.A. Turbofan Engines
CFM International S.A. Turbofan Engines
This AD applies to CFM International S.A. (CFM) CFM56-5B engines with turbine rear frame (TRF), part number (P/N) 338-102-907-0 or P/N 338-102-908-0, installed.
We are adopting a new airworthiness directive (AD) for certain CFM International S.A. (CFM) CFM56-5B series turbofan engines. This AD was prompted by a corrected lifing analysis by the engine manufacturer that shows the need to identify an initial and repetitive inspection threshold for certain part number (P/N) turbine rear frames (TRFs). This AD requires initial and repetitive inspections of certain P/N TRFs on the low-pressure turbine (LPT) frame assembly. We are issuing this AD to prevent failure of the TRF on the LPT frame assembly, which could lead to engine separation, damage to the engine, and damage to the airplane.
(1) For Engines that have Applied CFM Service Bulletin (SB) No. CFM56-5B S/B 72-0308:
(i) Prior to accumulating 25,000 cycles since new (CSN) on the TRF of the LPT frame assembly or within 150 cycles after the effective date of this AD, whichever occurs later, perform an initial eddy current inspection (ECI) or a fluorescent penetrant inspection (FPI) of the TRF mount struts on the LPT assembly.
(ii) For engines with unknown CSN on the TRF of the LPT frame assembly, perform the initial inspection required by this AD within 150 cycles-in-service (CIS) after the effective date of this AD.
(iii) Use paragraph 3.B. in the Accomplishment Instructions of CFM SB No. CFM56-5B S/B 72-0850, dated December 19, 2012, to do the ECI and paragraph 3.C. in the Accomplishment Instructions of CFM SB No. CFM56-5B S/B 72-0850, to do the FPI. Do not include TRF mount strut crack lengths towards the cumulative crack length after the cracks are repaired.
(iv) If no cracks are found on any of the three TRF mount struts, repeat the inspection within 1,670 cycles since last inspection (CSLI) or prior to accumulating 25,000 CSN on the TRF of the LPT assembly, whichever occurs later.
(v) If the cumulative length of all cracks found at any TRF mount strut location is less than 0.20 inches, repeat the inspection within 1,670 cycles CSLI.
(vi) If the cumulative length of cracks found at any TRF mount strut location is greater than or equal to 0.20 inches, but less than 0.25 inches, repeat the inspection within 280 CSLI.
(vii) If the cumulative length of cracks found at any TRF mount strut location is 0.25 inches or greater, replace the TRF with a part eligible for installation before further flight.
(2) For Engines that have Not Applied CFM SB No. CFM56-5B S/B 72-0308:
(i) Prior to accumulating 32,000 CSN on the TRF of the LPT frame assembly or within 150 cycles after the effective date of this AD, whichever occurs later, perform an initial ECI or FPI of the TRF mount struts on the LPT frame assembly.
(ii) For engines with unknown CSN on the TRF of the LPT frame assembly, perform the initial inspection required by this AD within 150 CIS after the effective date of this AD.
(iii) Use paragraph 3.B. in the Accomplishment Instructions of CFM SB No. CFM56-5B S/B 72-0850, dated December 19, 2012, to do the ECI and paragraph 3.C. in the Accomplishment Instructions of CFM SB No. CFM56-5B S/B 72-0850, to do the FPI. Do not include TRF mount strut crack lengths towards the cumulative crack length after the cracks are repaired.
(iv) If no cracks are found on any of the three TRF mount struts, repeat the inspection within 2,500 CSLI or prior to accumulating 32,000 CSN on the TRF of the LPT assembly, whichever occurs later.
(v) If the cumulative length of cracks found at any TRF mount strut location is less than 0.20 inches, repeat the inspection within 2,500 CSLI.
(vi) If the cumulative length of cracks found at any TRF mount strut location is greater than or equal to 0.20 inches and less than 0.25 inches, repeat the inspection within 370 CSLI.
(vii) If the cumulative length of cracks found at any TRF mount strut location is 0.25 inches or greater, replace the TRF with a part eligible for installation before further flight.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
